This invention relates to marine risers for deep subsea drilling and production and in particular to a coupling assembly therefor.
Marine risers are run from floating vessels or platforms to subsea wellheads for drilling and production operations. The riser sections are tubular, in the order of 20 inch diameter and 50 feet long. They are assembled at the surface and are run from the vessel to the wellhead. In assembling these, a successive section is first stabbed into a preceding section and the connector then bolted up. Accordingly, easy stabbing is desired.
The riser is usually highly tensioned at the upper end to avoid buckling and is also subject to cyclical bending caused by current and/or vessel drift. The riser must remain leak tight over its life to prevent ingress of sea water and/or leakage of mud during drilling, and potential oil during production. This despite the cyclical loading placed thereon.
Handling of large risers sections can cause damage to the couplings. A design tolerant of such damage and/or one easily repaired is therefore desirable.